title: Mannuronan C-5 epimerases suited for tailoring of specific alginate structures obtained by high-throughput screening of an epimerase mutant library.
abstract: The polysaccharide alginate is produced by brown algae and some bacteria and is composed of the two monomers, β-D-mannuronic acid (M) and α-L-guluronic acid (G). The distribution and composition of M/G are important for the chemical-physical properties of alginate and result from the activity of a family of mannuronan C-5 epimerases that converts M to G in the initially synthesized polyM. Traditionally, G-rich alginates are commercially most interesting due to gelling and viscosifying properties. From a library of mutant epimerases we have isolated enzymes that introduce a high level of G-blocks in polyM more efficiently than the wild-type enzymes from Azotobacter vinelandii when employed for in vitro epimerization reactions. This was achieved by developing a high-throughput screening method to discriminate between different alginate structures. Furthermore, genetic and biochemical analyses of the mutant enzymes have revealed structural features that are important for the differences in epimerization pattern found for the various epimerases.
authors.affiliation: Department of Biotechnology, SINTEF Materials and Chemistry, Trondheim, Norway. Anne.Tondervik@sintef.no
authors.forename: Anne
authors.initials: A
authors.lastname: Tøndervik
authors.forename: Geir
authors.initials: G
authors.lastname: Klinkenberg
authors.forename: Finn L
authors.initials: FL
authors.lastname: Aachmann
authors.forename: Britt Iren Glærum
authors.initials: BI
authors.lastname: Svanem
authors.forename: Helga
authors.initials: H
authors.lastname: Ertesvåg
authors.forename: Trond E
authors.initials: TE
authors.lastname: Ellingsen
authors.forename: Svein
authors.initials: S
authors.lastname: Valla
authors.forename: Gudmund
authors.initials: G
authors.lastname: Skjåk-Bræk
authors.forename: Håvard
authors.initials: H
authors.lastname: Sletta
mesh_terms: D000464:Alginates / Q000737:chemistry*; D019943:Amino Acid Substitution; D016948:Azotobacter vinelandii / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002238:Carbohydrate Epimerases / Q000737:chemistry* / Q000235:genetics; D020134:Catalytic Domain; D057075:Enzyme Assays; D004926:Escherichia coli; D006603:Hexuronic Acids / Q000737:chemistry; D057166:High-Throughput Screening Assays; D007700:Kinetics; D008351:Mannans / Q000737:chemistry; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D013237:Stereoisomerism
chemical_list: D000464:Alginates; D001426:Bacterial Proteins; D006603:Hexuronic Acids; D008351:Mannans; D002238:Carbohydrate Epimerases; C086519:mannuronan c-5-epimerase